The present invention relates to a freewheel to be used for the motive power transmission mechanism of vehicles, such as bicycles and motorcycles, and other machines.
In the conventional freewheel of this kind, a sprocket wheel having teeth at its periphery for engagement with a chain is provided at its inner circumferential surface, with saw-toothed ratchet teeth, and on a part of the periphery of the body which is fitted in the sprocket wheel there are provided pins which are always urged to protrude by a spring so that tips of the pins are brought into contact with the ratchet teeth. Under this arrangement, when the sprocket wheel is rotated in one direction, the body is rotated together with the sprocket wheel by engagement of the pins with the ratchet teeth, and when the wheel is rotated in the other direction or when the sprocket wheel rotates at a speed higher than the r.p.m. of the body, the pins are disengaged from the ratchet teeth so that the sprocket wheel rotates independent of the body.
In the above conventional method, in order to provide pins and ratchet teeth at the outer circumferential surface of the body, the body must have a comparatively large size. On the other and, a wheel having a smaller size raises problems with regard to manufacture and strength.